1. Field of the Invention
Embodiments of the invention generally relate to methods and apparatuses for depositing materials on a substrate, and more specifically, to methods and apparatuses for depositing high-k dielectric materials by vapor deposition processes.
2. Description of the Related Art
In the field of semiconductor processing, flat-panel display processing or other electronic device processing, vapor deposition processes have played an important role in depositing materials on substrates. As the geometries of electronic devices continue to shrink and the density of devices continues to increase, the size and aspect ratio of the features are becoming more aggressive, e.g., feature sizes of 0.07 μm and aspect ratios of 10 or greater are being considered. Accordingly, conformal deposition of materials to form these devices is becoming increasingly important.
While conventional chemical vapor deposition (CVD) has proved successful for device geometries and aspect ratios down to 0.15 μm, the more aggressive device geometries require an alternative deposition technique. One technique that is receiving considerable attention is atomic layer deposition (ALD). During an ALD process, reactant gases are sequentially introduced into a process chamber containing a substrate. Generally, a first reactant is pulsed into the process chamber and is adsorbed onto the substrate surface. A second reactant is pulsed into the process chamber and reacts with the first reactant to form a deposited material. A purge step is typically carried out between the delivery of each reactant gas. The purge step may be a continuous purge with the carrier gas or a pulse purge between the delivery of the reactant gases.
The formation of high-k dielectric materials by oxidizing metal and silicon precursors during an ALD process is known in the art. Ozone or atomic oxygen is a common oxidant or oxidizing source for ALD processes. A low process temperature may be advantageously maintained during the deposition process while forming the dielectric material due to the radical state of ozone and atomic oxygen. While the high reactivity at low temperature is an attribute of the radical oxidizing agents, undesirable side reactions are prevalent throughout the process chamber forming contaminants on the substrate. Alternatively, water or oxygen may be used as an oxidizing source to form dielectric materials during an ALD process. However, due to the moderate reactivity of water or oxygen, ALD processes generally require slower flow rates, longer exposure periods and higher temperatures than radical oxygen sources. Also, ALD processes that use water or oxygen require an extended purge period after each oxidizing pulse and therefore increase fabrication throughput. Furthermore, the slow flow rates and high temperatures usually increase contaminants on the substrate surface.
Steam oxidation processes have been used to passivate or oxidize metal or silicon materials during conventional CVD processes. In one example, water vapor is plumbed into the process chamber after being generated by boiling water contained within a secondary container. In another example, hydrogen gas and oxygen gas are fed into a process chamber preheated at a high temperature (e.g., >1,000° C.). In both examples, the generated water vapor reacts with a metal surface or a silicon surface to form dielectric materials, such as metal oxides or silicon oxides. While the aforementioned steam oxidation processes may produce an effective water vapor for use during a CVD process, the generated water vapor is not acceptable for use during an ALD process. Water vapor derived from these steam oxidation processes may cause contaminants on the substrate surface and modest control over process temperature or the contents of the oxidizing water vapor. Also, ALD processes require immediate access to reagents of a consistent composition that may be quantitatively delivered into the process chamber.
Therefore, there is a need for an apparatus and a process for depositing a dielectric material that generates an oxidizing gas at low temperatures, controls the composition of the oxidizing gas and the deposited dielectric materials, shortens process periods and minimizes contaminants.